The present invention pertains to a camera having a temporary storing circuit for temporarily storing control data during loading and unloading of a film case to protect the control data from the effects of static electricity, power disruption or external noise.
In order to automatically adjust the operation of a camera depending on the particular film installed, the film case is provided with a conductive pattern which indicates the film sensitivity. The camera automatically reads the film sensitivity from the installed film case and sets suitable exposure conditions in accordance with the read sensitivity. The film case is installed by opening a back cover of the camera and placing the film case in the camera at a predetermined position. Once installed, the conductive pattern on the surface of the film case comes into electrical contact with a plurality of sensitivity detection terminals (DX terminals) provided in the camera. The film sensitivity is determined based on which ones of the DX terminals contact the conductive pattern, wherein different conductive patterns on the film case indicate different film sensitivities.
The conductive pattern can be formed by painting a conductive paint onto the surface of an insulated portion of the film case. Individual terminals of the plurality of DX terminals that contact the conductive paint pattern conduct electric current whereas the DX terminals which do not contact the conductive paint pattern do not conduct electric current. Alternatively, the pattern can be painted using an insulating paint formed on a conductive surface of the case. DX terminals which do not come in contact with the pattern of insulating paint will conduct electric current whereas DX terminals that do come into contact with the insulating paint will not conduct electric current. In this way, the film sensitivity can be determined by detecting the particular pattern of conductivity of the DX terminals and the operation of the camera can be set according to the film sensitivity.
A drawback of the conventional camera is that while the back cover is open and the film is being installed, static electricity accumulated on the body of the user may be input to the DX terminals, either directly by touching the terminals or through a conductive portion of the camera case. This static electricity causes a large voltage to be applied to a control circuit of the camera, which may result in damage or malfunction. Even if resistors of high resistance are connected to the DX terminals, there is the possibility that the high voltage will destroy the control circuit or cause a malfunction. Moreover, if the control circuit includes a reset circuit, then a voltage detector within the reset circuit will detect that the high voltage is in excess of a predetermined voltage, and the reset circuit will operate to erase the various settings (the contents of the control circuit memory) and the control circuit will be initialized.
As a result, the static electricity received by the DX terminals can disrupt the settings of the control circuit, such as the photographing mode (normal photographing, backlight photographing, continuous photographing, multiple exposure, self-timer, etc.) and the strobe mode (automatic flash, manual flash, red-eye reduction, etc.), causing the camera to operate improperly.
Furthermore, if a general purpose microcomputer is used as a CPU for the camera, the high voltage static electricity may disrupt a setting which determines whether a particular terminal is an input terminal or an output terminal, thus making photography impossible.